I recently had the same problem with the stiches on a small quilt I made (actually I've always had that problem to one extent or another). My latest quilt I changed over to a cotton batting. Worked sooooo much better. the layers held together so much better and used less pinning. The stitches were much more even and looked so much better. Hope you are able to get it going soon. I know how frustrating it can be.
Linda